Overround / Margin Calculator
Calculate the bookmaker margin in any market and see the fair odds with the margin removed.
Last updated
Quick answer
Add up the implied probabilities of every outcome (1 ÷ decimal odds). The amount above 100% is the overround. For 2.10 / 3.40 / 3.60, the book is 47.6% + 29.4% + 27.8% = 104.8%, so the overround is 4.8% and the bookmaker margin is about 4.6%.
Overround / Margin Calculator
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- Definition Overround
- The total implied probability of every outcome in a market, minus 100%. It represents the bookmaker’s built-in edge.
Fair odds
The calculator removes the margin proportionally from each outcome to show “fair” odds — a useful benchmark, though bookmakers do not always spread their margin evenly.
Why it matters
The same match can carry very different margins at different bookmakers. Lower-margin markets return more to bettors over time.
Frequently asked questions
What is a good bookmaker margin?
Lower is better for bettors. Major football match-odds markets often carry lower margins than niche or in-play markets.
Is margin the same as overround?
They are closely related. Overround is the book total above 100%; margin is the share of stakes the bookmaker expects to keep: 1 − 1 ÷ book.